The present invention relates to an arrangement for controlling the rate at which a source supplies electric energy into a circuit, in general, and more particularly to such an arrangement which is used in an electroplating installation to control the rate of the electroplating operation which is being performed therein.
Electroplating installations per se are already known and are being widely used in various fields of human endeavor to improve either the mechanical or chemical properties, or the appearance, of a wide variety of objects, articles or workpieces. Basically, an electroplating installation includes at least one electroplating vat which accommodates an electroplating bath and is equipped with electrodes, and a carrier on which the workpiece or a plurality of workpieces is supported for the duration of the electroplating operation. In many instances, the carrier is removably mounted or supported on the electroplating vate so that the workpieces can be introduced into and removed from the electroplating bath together with the carrier which supports the same. Under these circumstances, it is very advantageous, in order to facilitate the handling of the carrier, if the latter is only supported on the electroplating vat by means of pins or the like which are introduced from above into the associated and cooperating support arrangements provided on the electroplating vat. The present invention is intended to be employed in an electroplating installation of this type.
The operation of an electroplating installation is also too well known to require any protracted discussion here. Suffice it to say that a source of direct electric current is employed which supplies electric energy into an electric circuit of the electroplating installation which includes the above-mentioned electrodes and, more often than not, also the carrier for the workpieces. In other words, usually the electric current flows through the carrier, rather than only passing through the workpieces and bypassing the carrier. When electric current flows in the above-mentioned circuit, metal is being deposited on the workpieces at a rate which is determined by the voltage or the intensity of the direct electric current supplied to the electroplating installation by the electric source. It is also well known that the proper control of the above-mentioned parameters of the electric current is determinative of the quality of the metallic layer deposited on the workpieces during the electroplating operation. The above-mentioned parameters of the electric current must not be too high for the respective workpieces to be electroplated inasmuch as the deposited metallic layer would otherwise be faulty; on the other hand, these parameters should also be as high as possible in order to achieve that the electroplating operation is performed in a feasibly short period of time.
When workpieces of always the same type and thus of always the same surface area are being treated in the electroplating installation or in the particular electroplating vat all the time, the control of the above-mentioned parameters can be achieved, for instance, manually only once and the adjusted magnitude of these parameters may then remain unchanged. However, very often different types of workpieces are to be treated after each other in the electroplating installation so that frequent control of the intensity or of the voltage of the direct electric current so as to take into account the properties of the respective workpieces to be electroplated in the electroplating installation, is unavoidable. When this is done manually by the operating personnel, this is very time-consuming and hence expensive.
In order to save this expense, it has been already proposed to provide variable markings on the carrier for the workpieces to be electroplated. In the event that the workpiece carrier is to be transported into the electroplating installation, the above-mentioned markings are adjusted at the location at which the workpieces are introduced thereinto to correspond to the properties of the workpieces to be electroplated. This pre-set marking is then transmitted, at the respective electroplating station or vat, for instance, to terminal switches or to non-contact switching devices. Then, a control device of the source, such as of a rectifier, has a certain value of electric voltage or electric current associated with each of the adjusted positions of the markings on the workpiece carrier. Then, the rectifier which is equipped with an electric setting drive, is automatically set to the above-mentioned value.
However, experience with the above-discussed arrangements of this type which are equipped with a pre-selection of the setting of the rectifier on the workpiece carrier, has shown that they are possessed of a very important disadvantage which resides in the fact that the setting of the rectifier output is possible only on a step-by-step basis. Furthermore, the required voltage or intensity value has to be first associated with one of the above-mentioned steps, which renders it possible that such an association could be erroneous. Also, as the demand for a possibly closest approximation of the pre-selected value to the optimum value for treating the respective workpieces is increasing, the number of the different adjusting possibilities also considerably increases which renders the operation of this arrangement increasingly difficult.